Recombining
I was a little unclear on the recombining, especially since I had burned the 3 files I got from my split onto DVDs and moved them to another computer, but after figuring it out, I thought it would help people like myself who lack any real skills at using Terminal to type out an (over)explanatory description of how to do it.
Make sure all your files are in one folder, preferably by themselves. In my case I had three files, each about 2GB, named "xaa", "xab", and "xac".
Open Terminal.
Type "cat " (no quotes, include the space)
Drag the first file into Terminal, next to where you just typed "cat ". This should add the directory location of the file.
Now press delete a couple times so that you're left with only the first letter of the file name. So in my case I'm deleting "aa" from "xaa" so I'm left with only "x".
Now type "* >" (no quotes include the space)
Finally type the original file name. VERY IMPORTANT! If there are any spaces in the file name, add "\" (no quotes) before the space. So if you're filename was:
Software I Downloaded Illegally.dmg
you would need to type:
Software\ I\ Downloaded\ Illegally.dmg
That last part is important!
In my case it didn't create the recombined file in the same folder, it dumped it in my Home folder. Not sure why it did that, but that's probably where you're file will be.